Hospitals and other healthcare facilities often administer food and/or medications to patients via an administration set such as a feeding tube when those patients are unable to take food and/or medications by mouth due to, for example, an inability to swallow. Typically, fluid is delivered to the patient by a pump set loaded on a flow control apparatus, such as a peristaltic pump, which delivers fluid to the patient at a controlled rate of delivery. A peristaltic pump usually comprises a housing that includes a rotor or the like operatively engaged to at least one motor through a gearbox. The rotor drives fluid through tubing routed through the pump set by the peristaltic action effected by rotation of the rotor by the motor. The motor is operatively connected to a rotatable shaft that drives the rotor, which in turn progressively compresses the tubing and drives the fluid at a controlled rate through the pump set. The pump set may have a type of valve mechanism for permitting or preventing fluid flow communication through the pump set. A controller operates the motor or motors used to drive the rotor and, if necessary, controls fluid flow by operation of the valve mechanism.
It is important to monitor the administration of such enteral nutritional fluids being supplied to a patient via a feeding tube to ensure that the patient receives a correct dose of medication and/or a sufficient amount of nutritional fluids. For example, it is important to have the ability to detect whether or not air is the feeding tube, which can be indication whether or not nutritional fluids or medications are being delivered to the patient.
Conventional administration sets often include a drip chamber that is connected between the pump and the patient. As known to those skilled in the art, the drip chamber includes a container typically made from a clear resilient plastic material that allows pinching or squeezing of the container. The drip chamber has associated tubing, which connects the drip chamber into fluid communication with a medical device (e.g., bag or pump) or some other form of apparatus used to control the infusion to a patient and into fluid communication with to a section of tubing delivering fluid to the patient. In an operable state, the drip chamber is partially filled with fluid to establish a fluid level that is somewhere near the midpoint of the container.
Such conventional administration sets often include a fluid level detector associated with the drip chamber for the purpose of monitoring the level of fluid in the drip chamber and, thus, the fluid being delivered to the patient. Unfortunately, the circuitry of such detectors can be quite complex. For example, such fluid level detectors often require circuitry for generating and sensing multiple light paths with respect to a particular expected fluid level in the drip chamber. Moreover, because there are multiple sensing components, such detectors often require the execution of complex algorithms to calculate the fluid level in the drip chamber. Moreover, the drip chamber introduces another component into the administration set, which in addition to adding expense and being altitude dependent, has the potential to fail and, thus, interrupt the delivery of fluid to a patient.
Light to voltage (LTV) converters have been used as fluid detectors for the purpose of monitoring the presence of fluid in the drip chamber. In operation, a light source positioned on one side of the drip chamber transmits a beam of light through the drip chamber and onto a LTV converter positioned on an opposite side of the drip chamber. The LTV converter is responsive to the intensity of the transmitted light to generate a high or low voltage output signal. For example, when the transmitted light is substantially uninterrupted, the LTV converter generates a high voltage output signal. Alternatively, when the transmitted light is interrupted, the LTV converter generates a low voltage output signal. Accordingly, when fluid drips thru the light beam passing through the drip chamber, the light beam is interrupted and a low voltage output signal is generated. However, when the drip chamber is not present, for reasons such as described above, the LTV converter cannot be used to detect fluid flow directly in the feeding tube because of a lack of detectable transitions (e.g., drips) within the feeding tube. That is, in contrast to the drip chamber, there are no reoccurring air-to-fluid transitions when fluid is flowing in the feeding tube. Moreover, LTV converters are not effective in detecting clear fluids.